Powder feeding apparatus, electrostatic powder coating apparatus and powder flow-rate measuring apparatus

In combination, an electrostatic powder coating apparatus and a powder feeding apparatus in which powder is fed through a large-diameter powder feeding duct by a carder gas supply means, said powder feeding apparatus comprising:

• a means for adjusting a portion of a carrier gas to a fixed flow rate and supplying said portion as a powder flow rate detection gas;
• a sensor nozzle which is provided on the downstream side of said means and through which said powder flow rate detection gas flows out;
• a powder flow rate measuring capillary which is provided on the downstream side of and in close proximity to said sensor nozzle which has an inlet and an outlet, and which has a diameter that is smaller than that of said large-diameter powder feeding duct;
• pressure difference measuring means which are connected to said inlet and said outlet through filter means for the purpose of measuring a pressure difference between the inlet and the outlet of said capillary and which constitute a blind pipe route having invariant interior volumes during normal operation;
• a means for introducing powder to the inlet of said powder flow rate measuring capillary;
• a large-diameter powder feeding duct connected to said capillary;
• a feeding rate adjusting gas supply means connected to said large-diameter powder feeding duct;
• a means for adjusting the pressure difference between the inlet and the outlet of said powder flow rate measuring capillary;
• and
• an electrostatic powder coating gun system connected to said large-diameter powder feeding duct of said powder feeding apparatus, said electrostatic powder coating gun system including a means for charging powder, a means for electrically driving powder toward an object to be coated, and a means for spraying powder.

A powder flow rate measuring apparatus comprising:

• a powder flow rate measuring capillary having an inlet and an outlet;
• a nozzle through which only a powder flow rate detection gas is blown into the inlet of said capillary;
• a means for controlling the flow rate of the powder flow rate detection gas supplied to said nozzle;
• a means for introducing powder to the inlet of said capillary;
• and a pressure difference measuring means consisting of a blind pipe route connected to said inlet and said outlet through filter means for the purpose of measuring a pressure difference between the inlet and the outlet of said capillary.

A powder feeding apparatus, comprising a sensor nozzle equipped with a flow rate control;

• a powder introducing passage;
• a high pressure duct, wherein an end of said sensor nozzle, an end of said powder introducing passage, and a base end of said high-pressure duct communicate with an inlet of a measurement capillary respectively;
• a large-diameter powder feeding duct whose diameter is larger than that of said measurement capillary which communicates with an outlet of said measurement capillary;
• a low-pressure duct having a base end which communicates with an outlet of said measurement capillary;
• a pressure differential detecting device which communicates with a tip of said high-pressure duct, and a tip of said low-pressure duct respectively, said pressure differential detecting device comprising a pressure sensing member with a high-pressure chamber and a low-pressure chamber on either side of said pressure sensing member, wherein said high-pressure duct, said low-pressure duct, said pressure sensing member, and said high-pressure chamber and said low-pressure chamber form a pressure differential detecting module.